Cave exploration -- or spelunking -- is an affordable, family-friendly activity that can feel like a bona fide adventure.
Spurred along by changes in the atmosphere involving wind, water, sand erosion and powerful shifts of earth, it can take thousands of years for caves to be carved out. Exploring them involves delving below ground for an up-close look at massive layers of rock, eerie formations of mineral deposits and other mysterious wonders, such as underground rivers.
You don't have to go far to find them.
At least a half-dozen large caves within a day's drive of Long Island are open to the public. And summer is an ideal time to explore -- cave temperatures average 50 degrees year-round, making them a welcome respite from sweltering temperatures above ground.
First-timers should opt for a basic tour that involves walking on lighted pathways or sitting in a boat for a narrated show-and-tell. You'll want to bring a light jacket and wear sturdy sneakers or hiking shoes.
More experienced spelunkers who don't mind getting dirty can opt for hands-on tours that call for maneuvering through tight spaces.
Here are six Northeast caves that offer various levels of exploration, as well as other activities nearby to round out a day trip.
255 Discovery Dr., Howes Cave, N.Y.
DISTANCE FROM NYC About 165 miles
WHEN TO GO Daily, year-round
This 6 million-year-old cavern is the largest that's open to the public in the Northeast -- it's also New York's second-most-visited natural attraction, after Niagara Falls. You'll feel "cave kisses" of moisture as you exit the elevator that takes you down 156 feet. The daily 80-minute traditional walking tour ($23 adults, $19 ages 12-15, $12 ages 5-11) leads you farther downward, through serpentine corridors, past stalagmites, dripping stalactites, flowstone and other huge formations such as Titan's Trumpet and Pipe Organ, to an underground boat ride on Lake Venus. The Winding Way is sculpted by excellent examples of multicolored erosion. More than 500 couples have been married on the illuminated heart-shaped bridal altar.
On weekend evenings, the shadowy two-hour lantern tour is an evocative way to explore the depths ($35, reservations required). The two-hour adventure tour sends visitors in coveralls, gloves and lighted helmets crawling through a passage, across a dry streambed and up a 107-foot-high dome of rock called the Great Rotunda ($108, includes gear rental).
WHILE YOU'RE THERE Howe Caverns has a new above-ground zip line and rope course ($10-$23) as well as kid-friendly diversions such as gemstone mining and selecting a geode (sphere-shaped volcanic rock) to crack open. An outdoor exhibit of 24 life-size dinosaurs is slated to open in 2013.
Natural Stone Bridge and Caves Park
535 Stone Bridge Rd., Pottersville, N.Y.
DISTANCE FROM NYC About 230 miles
WHEN TO GO Fridays-Sundays and Wednesdays July 1- Aug. 31 (self-guided tours Memorial Day-Oct. 12)
The East's largest marble cave entrance leads to what is said to be some of North America's oldest rocks, where you can see tourmaline and garnet in the walls. A summer-only four-hour adventure tour involves wading and crawling through tight, billion-year-old surface caves before passing through a waterfall into a river and floating down a tunnel of caves ($80, ages 13 and older).
Less rigorous are self-guided walking tours of rock sites mostly above-ground, such as a massive stone bridge arch, several cave entrances, waterfalls and a gorge. The stone step trail requires climbing stairs and is not suitable for strollers. Plan to spend about an hour on the 3/4-mile trail ($12.98 adults, $8.50 ages 5-12).
WHILE YOU'RE THERE Kids can play games ranging from climbing a "boulder" wall to exploring the crystal mine or digging for dinosaur bone casts. There's also a nine-hole flying disc "golf" course.
200 Caverns Park Rd., Farmington, Pa.
DISTANCE FROM NYC About 350 miles
WHEN TO GO April 30-Oct. 31
Pennsylvania's largest cave is set below a 435-acre geological park. This is a sandy cave with slight seepage. You'll see 3 million years of limestone layers. A one-hour "family tour" takes you down 170 feet on steps and a slanted floor for a 1/2-mile walk ($11 adults, $8-$9 school-age children).
More challenging is the "upper spelunking" tour -- a three-hour look at the more geologically developed parts of the cave. Participants must be at least 9 years old and wear long pants and a long-sleeve shirt for protection while crawling up and over rocks along the way ($16, reservations required). The most intense experience is the "lower spelunking" tour. Offered weekends only, it takes visitors ages 12 and older down 45 stories of rock into caves that are developed and still forming ($22).
WHILE YOU'RE THERE For something fun and different, try controlled rappelling. You'll be harnessed for the three drops off the lighted cliff inside the cave ($33, available Memorial Day-Labor Day).
Lost River Caverns
726 Durham St., Hellertown, Pa.
DISTANCE FROM NYC About 80 miles
WHEN TO GO Daily (except holidays) year-round
Set in the Lehigh Valley, this 250,000-year-old limestone cavern has five chambers, with crystals, that can be explored on foot. Besides stalagmite and stalactite formations, you'll see mineral growths and rock formations that seem to defy gravity.
Ultraviolet light illuminates colorful fluorescent minerals that glow in the dark. Another unique feature is the clear underground Lost River, which flows seemingly without beginning or end. Cave tours cost $11 ($7 ages 3-12).
222 Penns Cave Rd., Centre Hall, Pa.
DISTANCE FROM NYC About 225 miles
WHEN TO GO Daily March-November, weekends in December
Set in an Amish valley, Penn's Cave is a cavern that must be traversed by boat, combined with a topside wildlife park. Rich in Native American history and folklore, the cavern is listed on the National Register of Historic Places. Walk down 48 steep steps to the cave entrance and board a motorboat for the hourlong cave tour ($16.50 adults, $8.75 ages 2-12).
You'll pass through narrow tunnels and rooms to see flowstone, drapery, pillars and column formations. Other huge formations resemble the Statue of Liberty and Rock of Gibraltar. The tour emerges into man-made Lake Nitanee for a glimpse of grazing deer and elk.
WHILE YOU'RE THERE Pair the water tour with a 90-minute guided drive and stroll through the 1,500-acre wildlife park and working farm ($30.95 adults, $16.95 ages 2-12).
Lost River Gorge and Boulder Caves
1712 Lost River Rd., Route 112W, North Woodstock, N.H.
DISTANCE FROM NYC About 375 miles
WHEN TO GO May 14-Oct. 23
Lost River is a boulder cave with 11 chambers under and between a tumble of gigantic granite slabs formed 300 million years ago in the rugged White Mountains. The self-guided daily tour ($16 adults, $12 ages 4-12) leads you 300 feet down into a gorge. You'll walk a 3/4-mile loop along a boardwalk overlooking the river, past waterfalls, including 35-foot Paradise Falls. Along the way, you may climb into caves such as the Dungeon or Lemon Squeezer.
A new section of boardwalk over Paradise Falls brings you to a scenic mountaintop high above the gorge, river, granite pothole and vernal pool. Saturday evenings, you may do this tour with a guide by lantern light and headlamp followed by s'mores around a fire ($25 adults, $20 ages 4-12).
WHILE YOU'RE THERE Above ground, hike the 1/2-mile ecology trail and visit a garden with 300 varieties of plants.